One square foot equals 0.0929 square meters. So to convert from square feet to square meters, just multiply by 0.0929.
So let's say you're in the United States, and you've purchased a home that's 2,030 square feet. You're trying to tell your friend in London about the home, and how big it is.
2030 x 0.0929 = 188.587
So your 2,030-square-foot house is equal to 188.587 square meters. (If you say it's 188 square meters, he'll get the idea.)
To convert from square meters to square feet, simply divide the number of square meters by 0.0929 to get the number of square feet.